The principal purpose of this Core is to provide a common facility and expertise for the broad spectrum of morphologic studies that may be required for interpretation of gene therapy studies. Additional major functions of this Core includes the development of antibodies and DNA and RNA probes that may be useful for the identification of cell types or localization of molecules of interest in normal and genetically manipulated tissues, and the development of enhancements to existing morphologic techniques that will improve the ability of Center investigators to localize specific molecules in tissue sections. The principal morphologic techniques provided by this Core include routine histology, including special histologic stains, immunohistochemistry, immunofluorescence microscopy, tissue enzyme histochemistry, electron microscopy, immunoelectron microscopy, in situ hybridization, and necessary ancillary techniques such as Western, Southern and Northern blotting and antibody binding and competitive inhibition assays needed to ensure the sensitivity and specificity of all proposed procedures.